More people are contracting Hib infection despite a child vaccination programme, government advisors warn.

Rates of the meningitis-causing bacteria among adults have reached levels higher than before 1992, when routine vaccination of babies started.

Rates in children are also rising, mainly among those immunised as babies, according to Health Protection Agency (HPA) experts.

Booster jabs should reduce rates they told the British Medical Journal.

Resurgence

Hib is the term commonly used to describe a disease caused by the bacteria Haemophilus influenzae type b.

As well as meningitis, it can cause infection in joints, pneumonia and epiglottitis (swelling of part of the windpipe causing noisy, painful breathing and even blockage of the airway).

The Hib vaccine was introduced into the routine immunisation programme for babies in 1992, and led to a big reduction in Hib infection rates and deaths.

However, a number of factors, including problems with the type of vaccine used at the time, led to a drop in its effectiveness, and a corresponding rise in cases of Hib, according to the HPA.

We fully supported the implementation of a booster jab, and this report demonstrates that quick action will once again contribute to a fall in cases

Philip Kirby, chief executive of the Meningitis Trust

From 1998, Hib cases in children started to rise significantly, almost doubling each year and mostly among those who were immunised in the programme as babies.

To combat this rise, the Department of Health launched a Hib booster campaign between May 2003 and January 2004, targeting all children aged from six months up to four years.

Following this campaign, the number of cases reported fell in the age groups vaccinated.

But a smaller decline occurred in older children and in adults.

Booster

Rates of adult Hib infection are now higher than they were before the vaccination was introduced, say the HPA researchers.

There were 0.27 cases per 100,000 in 2003, compared with 0.17 in 1992.

Dr Mary Ramsay from the HPA's immunisation department, who led the research, blamed the introduction of the Hib vaccine in 1992 for the rise in adult cases.

"The drop in infection rates among children meant reduced exposure to the disease for adults, and therefore lower rates of infection.

"This means that the level of antibodies in adults, to enable them to fight Hib infection, was no longer being boosted.

"Therefore, as the disease started to rise once again amongst children, some adults were less able than before to fight the infection."

But Dr Ramsay said the booster campaign should help by increasing so called "herd immunity" - the fact that others in a herd or population have been vaccinated provides protection to all others, whether or not they are vaccinated themselves.

"This gradual increase in "herd immunity" will lead once again to a continuation of the fall in disease rates," she said.

Philip Kirby, chief executive of the Meningitis Trust, said: " We fully supported the implementation of a booster jab, and this report demonstrates that quick action will once again contribute to a fall in cases."

The Department of Health said it would continue to monitor the impact of its vaccination programmes, and seeks expert advice on whether the current immunisation programmes need to be modified to maximise protection.